1. Field of the Invention
The present invention relates to a controller for a motor used as a driving force generation element or the like for a vehicle, and a vehicle mounted with the motor.
2. Description of the Related Art
Generally, a motor having an armature of multiple phases, such as a brushless direct-current motor of three phases, is mounted in a vehicle such as a hybrid vehicle or an electric vehicle and is used as a driving force generation element for the vehicle. The operation control of the motor is generally performed by supplying electric power from a capacitor such as a battery or the like through the intermediary of an inverter (PWM inverter) circuit of multiple phases to the motor (for example, refer to Japanese Patent Laid-open No. H9-46811).
In general, the inverter circuit designated by a reference number 7 has a circuit configuration illustrated in FIG. 1, for example. As illustrated, the inverter circuit 7 is constituted by connecting in parallel arms 10u, 10v and 10w of multiple phases (3 phases in the illustrated example). Each of the arms 10u, 10v and 10w is constituted by connecting in series a switch portion 13a disposed on a positive polarity side and a switch portion 13b disposed on a negative polarity side. The switch portion 13a is constituted by connecting a switch element 11a and a feedback diode 12a in parallel. The switch portion 13b is constituted by connecting a switch element 11b and a feedback diode 12b in parallel.
When the motor is in operation, a short-circuit failure may occur in either switch portion of the inverter circuit so that the switch portion is kept in a continual conducted state despite a control signal output to a switch element of the switch portion. The conducted state of a switch portion described in the present invention means that both terminals of the switch portion are substantially short-circuited and an electric current can flow in the switch portion in both directions. When a switch element and a feedback diode of a switch portion are functioning normally, the conducted state of the switch portion is equivalent to the conducted state (ON state) of the switch element. Moreover, a short-circuit failure state of the switch portion means that the switch element of the switch portion is switched on (conducted state) continuously despite a control signal output to the switch element, or a feedback diode is in the conducted state in both directions, namely, a forward direction and a backward direction thereof.
When a short-circuit failure occurs, if the ON/OFF (conduction/disconnection) control of switch elements in a normal switch portion other than the switch portion occurred with the short-circuit failure is continued, there arises a problem that an excess electric current would flow in the switch portion or the like where the short-circuit has occurred according to an electromotive force occurred in each phase of the motor.
In this regard, the art disclosed in Japanese Patent Laid-open No. H9-46811 disposes a switch in a power distribution path between the capacity and the inverter circuit and a power distribution path between the inverter circuit and the motor. According thereto, when a short-circuit failure occurs in either switch portion of the inverter circuit, it is possible to prevent the electric current from flowing into each switch portion of the inverter circuit by, for example, shutting off the switches thereof.
However, according to the art disclosed in Japanese Patent Laid-open No. H9-46811, multiple switches would be necessary, and therefore, it is disadvantageous.